Genetic diversity among methicillin-resistant Staphylococcus aureus isolates carrying the mecC gene in Belgium.

ABSTRACT

OBJECTIVES: A mecA homologue gene, named mecC, has been reported in methicillin-resistant Staphylococcus aureus (MRSA) isolates from humans and from diverse animal species. We investigated the proportion, and the phenotypic and genotypic characteristics, of mecC-carrying MRSA recovered from humans in Belgium. METHODS: A total of 4869 S. aureus isolates, collected by the National Reference Centre from 2003 to 2012, were retrospectively analysed for the presence of mecC. The mecC-carrying MRSA isolates were tested for phenotypic resistance and the presence of toxin genes. Genotyping was performed using spa typing and multilocus sequence typing. RESULTS: Nine S. aureus isolates, mecA negative but cefoxitin resistant (MIC 16-64 mg/L), were found to carry the mecC gene. Among these, eight showed resistance to oxacillin (MIC 4-64 mg/L). These isolates remained fully susceptible to all non-ß-lactam antimicrobials. Although the proportion of mecC-carrying MRSA in Belgium was low (<1% per year), mecC-MRSA were assigned to three distinct genetic lineages corresponding to clonal complex (CC) 130, CC49 and CC1943. CONCLUSIONS: This first Belgian nationwide analysis showed a low occurrence of mecC-MRSA. Further studies should be conducted to better understand the reservoirs and risk factors for mecC-MRSA acquisition.